The present invention relates to a method and apparatus for flaring openings in cylindrical metallic bodies of relatively heavy gauge material which are to be utilized as sealed enclosures for gas insulated circuit breakers.
Presently known means for effecting the flaring of openings in metallic bodies are either a cold working procedure or a semi-hot working procedure. In the cold working procedure, flaring is accomplished by pulling a plurality of graduated dies, one at a time, through the opening to gradually enlarge the opening to a desired size. This procedure is time consuming and costly. If flaring of the opening is not accomplished, the opening would have to be cut into the tank and the operator tank to be subsequently fitted to the opening will require special forming to provide a saddle to mate with the contour of the enclosure tank. This is not acceptable in a power breaker enclosure for dielectric reason which requires a construction wherein all sharp corners are eliminated.
In the semi-hot working procedure, heat is not applied so that it follows the contour of the body being worked. As a result, grain growth and cold spots are experienced with cracking of the material around the flare developing. In either case, the cracks must be welded and the weld ground so that a smooth surface is obtained. This procedure is also time consuming and costly.